| Aluminum alloy has been widely used in aerospace, automobile manufacturing, shipbuilding and chemical industry by its small proportion, high intensity, good corrosion resistance, easy to process, rich resources and recyclable. The rapid development of the industrial economy expands the demand for aluminum alloy welded structure, which penetrates deeply aluminum welding study. On the line of car-body construction, resistance spot welding is one of the main connection technology. However, spot welding is extremely complex and a multi-physics coupling fields which contains thermal, electrical and structural process. The nugget formation is instantaneous and invisible, so that it is difficult for us to observe and research through traditional experiment. Additionally, aluminum has a feature of low resistivity and easy conductive, so the welding quality is poor. The process mechanism of aluminum alloy RSW is the key to solve the problem of spot welding. This paper researched the welding mechanism of the resistance spot welding for aluminum with a thickness of 1.6mm.Firstly, a preloading contact axisymmetric finite element was created by FEM and initialized conducting region is decided by this model; secondly, The thermo-electricity transient and thermal elastic-plastic mechanism of resistance spot welding for aluminum alloy were analyzed by indirect coupling method and thermal elastic-plastic theory. By analyzing temperature of welding field, the appearance and size of nugget were obtained. The shunt phenomenon in the multi-spots welding was existed for welded spot, so the heat would be significantly reduced and the strength of welded spot became poor. Numerical simulation of different spot distance of aluminum alloy spot welding was researched by this paper, the analysis result indicate : with the increasing of spot distance, the shunt rates would decrease and the size of nugget decreased slowly. To meet the conditions of the nugget penetration rate, the aluminum spot welding workpieces of 1.6mm’s thickness has a minimum spacing of 17 mm with electric current of 38 KA and current length of 0.166 s, which provided a theoretical basis choosing the spot distance. Finally, static tensile-shear found that the maximum tensile-shear loads of weldment of the same process parameters with numerical simulation compared with the theoretical value has been attenuated. As the distance decreased, the loads droped fastly, which demonstrated that shunt would influenced the strength of spot joint from macro aspect. Experimental results and simulations are in good agreement, which verify the simulation results is accurate. |
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